Need a measurement please 

From a deck stepped  carbon masted boat 

1: From the forestay mounting point on the hull to the mast - 

2: With a straight edge across the boat i.e a boom or similar sat across the decks how much above that level of the decks does the mast base start ?

3: From the lowest possible point in the boat how far up to get to the bottom of the mast 



Ive no fore deck for reference and the old space frame was made to match a trimmed down mast which is not the correct length -  and is falling apart so making a replacement hence the need for reference points -

Thanks very much in advance !

1. jib tack is as far forward as it will go
2/3.You need to find the sheerline point, (measurement in the rules 4 b,c,d & e )then there is a min and max height for the lower black band measured from the sheerline (rule 7 Cii) on the mast. where the foot is on the boat (Height)is different between designs.

Enjoy the rule reading

Having gone through this recently for Gannet the upper edge of the lower black band must be no more than 730mm above the sheerline and no less than 630mm from what I was given to understand.  I had to put an exra block of mahogany on Gannet's deck to raise the height of the mast, as the mast I had had been taken from a boat with a domed foredeck and thus with the flat foredeck I would have broken the minimum distance rule with my suit of sails.  Top and bottom distances are now fine.

Coner, I've just fitted a new mast to a local boat here at Starcross so have been through this process recently. The ref point is the shearline. This is the point at which the outside of the hull would intersect with the top of the deck. You need to make up a piece of card or plywood with a straight edge down one side and a gunwhale sized cutout on the same side. Bit difficult to explain in words... This enables you to work out where the hull would intersect the deck. Once you have the shearline marked on top of the deck (I used an OHP pen so it would rub off afterwards!) Put a straight edge across the top of the mast step (deck stepped)that extends out to both gunwhales (making sure it is right angles to the centreline of the boat) and measure from the bottom of the straight edge to the shearline point. Measure both sides and divide by 2. You can now measure from the top of the mast step to the top of the lower band. Add the 2 measurements together and this should be between 630mm and 730mm (rule 7cii)The lower black band is then your ref point on the mast from which all the other measurements are taken....
I've actually got a new carbon mast for sale if you're looking for one...

best of luck

Chris M and myself had a bit of a measure for 1) on a winder and on my wooden R&M Thin Ice a few days back.  There is a big difference (75mm or thereabouts) and I think the Winder mast was further forward.

As Chris pointed out at the time, the important relationship is between centre of effort of the rig (i.e. mast position fore and aft) and centre of lateral resistance of the foils (i.e. C'board position fore and aft - you can't do much about the rudder position!).

Although the winder mast position was further forward than the R&M mast, on both boats the centreboard bolt was the same distance back from the mast step.

Sorry, this doesn't help with dimensions, but it does suggest that the mast step to centreboard bolt position is a critical dimension - If I remember I'll measure my boat and post the distances.

Blimey thanks folks for the quick responses

I will digest these and see if i can figure out what you mean -  where can I get a copy of the rules on measurments ?

Its a NSM1 hull if anyone has already done the conversion

How much for the mast BTW ?

Cheers

Conor

Ref rules -  git it now via the link -  thanks had yet to click on first reply

Is this black band on the mast ?

This bits kind of trickey if it is as I have no mast :(

How far from the base of the mast is the black band were talking about

Many thanks again for the help

Conor

OK -  thanks all 

I think I get this now

If I know the distance from the base of the mast to the top of the first black ring then I can work out where my space frame needs to go to - 

I can still see where the hog stepped mast would have gone -  am I right in thinking that this position will still be right relative to the centerboard pin regardless of hog or deck stepping the mast ?

So if one of you kind folk could tell me the distance between the base of the mast and the top of the lower black ring I think Im sorted ;) :)

Many thanks again for the quick responses

Rgds

Conor

If memory serves, the Winder and Driver/Turner boats position their masts 53 inches from the jib tack. I thought The Trout's was further forward at about 49. It was a big differance.

I think the Winder board is further forward, but i've never measured one. There was a definate differance between my Driver boat and Jules' Ice. Also bear in mind that the bolt position on the board itself can vary. What you probably want is a measurement from the Jib tack to the front of the board rather than the pivot point.

What boat is this for by the way?

I deck-stepped my NSM 1 when Ally masts were still the norm.  

At the time there were at least two approaches:

Fill in the mast gate position (Vertically above the hog step) with a block of tufnol and mount the step directly above that.  In order to do this I had to put wood in from foredeck to hog to transfer the compression loads down. 

The foredeck of my boat (beautifully built by Lawrie Smart) was also highly domed when compared with the newer boats, and I failed to take that into account when I put my second-hand Superspars M1 on it. That had been taken from a newer, flatter foredecked boat (Coyote).  I had to chop around 70mm off the bottom to get it legal.

The Guy / Dave Winder approach as seen on ORAC, was very elegant. The original hog stepped mast was chopped at deck level, and then secured in place in the mast gate. This section did the job of transferring load to the hog. The main mast section was mounted directly on top of the 'stub' by some cunning rocker contrivance.  Minimal work required to ensure the black band remained in the same place!

A word of caution.  The increased loads of a modern raking rig have a profound effect on the brittle glue used in older hulls (3136 Substitute was built in 1979). After a season of sailing with the new rig, the hog parted company from the garboard planks on the outside of the hull, leaving a gap of c 3 to 4 mm for around 300mm in either direction fore and aft of the mast step position. Much glue required.

You should think about fitting some bracing to deal with the forces.

Conner.
I did a doc on wheat i did to deckstep a turner 2, the main measurement is from the transom to the rear face of the mast 2730mm, this came from a massive research at the time of all deckstepped boats, and even holds true on my present boat, as it was out,by 20mm, the differance in speed was very noticeable.

The Old Trout,


Quick question then. On some of the vintage boats that are deck stepped all there is to transfer the compression loads to the hog is a king post, I have also seen this on 1695 Ella which I believe was converted to deck step by Laurie, no low bouyancy tank conversion to stiffen the hull, why therefore do these boats not encounter problems of sprung planks through compression and dont require extra bracing, or do they? Maybe one for Mervyn to answer.

I reckon the rig tension is much lower than on the modern boats.  I know that Terrapin (no 36) uses a very low rig tension and if you look at her beating there is a huge curve on the luff wire of the jib (I have only once see this looking back at her as generally she is ahead of me!!!!!!).  John Gardiner says that if he increases the tension above this small amount she'll hardly point or go at all!!  It's also very difficult to get hefty tension onto the old arrangement jib halyard where the jib hanks to its own halyard and comes down the forestay and is cleated off on the deck. I have this arrangement on Secret Water.  No fancy Highfield lever in the old days nor muscle boxes etc.  Once you were set up for a sail that was it!!

My father put a low buoyancy tank into Fair Kop (1212) when converting her from hog to deck-stepped mast. But on his restoration of Crescendo (607) for Berry Ritchie no such front tank was put in despite the boat being converted to deck-step configuration.  He did, however, provide some extra lateral reinforcement by beefing up the bulkhead area (the actual detail of which is lacking on my part unfortunately).

Another modification to Fair Kop (despite the front tank) was to add lateral support struts, one each side of the boat in the cockpit between the plate case and the hull.  The idea was taken I think from John Harris's original Passing Cloud, as the plate case is relatively weak.

Sorry to hijack this post but is there any benefit in converting a vintage boat to deck step and if so what are the advantages?

Thanks

Richard

Richard

If you look in the Merlin book at the original Yachting World Article, you'll see that the very early boats had rotating deck stepped rigs!  Presumably at some point hog stepping was seen as the radical new departure, and the way to go!

re splitting planks - Good question.  I undestood that 3136 predated the onset of 'modern' epoxies.  A possible explanation is that in the perennial Merlin quest for lighter hulls,the technology of the day was stretched to its limit and hence more marginal strength in some locations. The older hulls presumably had heavier planks, and relied on clenched nails to compensate for cascamite glue.

I've no gripe with the quality of construction - 3136 was raced hard (if inexpertly) for the years that I had it.  To be honest, the separation of the hog from the garboard planks may have developed before the deck stepping. 

Jules

Many of the older boats have good bracing under the deck - effectively between the shrouds - and with narrower hulls there's less to fold up. Terrapin's mast also has multiple diamond wiring for stiffening.

As regards diamonds on the wooden mast Secret Water is the same - and rotating and as you say with the narrower hulls the forces are going to be more vertical than horizontal.  If there is high rig tension on the old deck stepped wooden masts then I think that we all find that the masts are difficult to rotate as they jam themselves into the socket of the ball and socket joint.  Vaseline and a one cent piece hammered to fit in the well seems to help.  Best use of US currency I feel!!!

It used to be traditional to put a Sovereign under newly stepped masts however with the price of Gold these days.

After scraping off a lot of varnish I found someone had glued a 1980 penny to the side of my mast step on 3245. Technically speaking it ought to be under the mast itself though.

Mags it must have been wonderful to find that your boat had doubled in value!!

Mags,

Did you leave it there like a coin in a cork or did you dare remove it!!??

Dave f 

was that from the transom itself or was it from a level line from the back of the mast to level with the transom 

All the loads will go through the space frame - we build race cars so I have a decent view of load management 

Boat is glass hull wooden decks and am in the process of carbon sheathing the decks too - it should be nice when its all done 

pics when Ive moved on a bit !

Conor

Thanks Garry, you cheeky sod. I left the penny in place of course.

Sorry to hijack the original thread....the only useful thing I can contribute is to watch out for the hull closing up (like a clamshell they say). There are two sets of deckstepping photos in the gallery.

Substitute was being built for me in the spring of 79, secretly, by Laurie in the deepest depths of the Sussex countryside. I wanted to try a dagger board, alla National 12's, which had proved quite quick that summer at the Burton Cup. Unfortunatly Phil Morrison paid a surprise visit to see Laurie and he popped down the workshop and saw, to his horror, what we were planning. Needless to say, he hotfooted it back to Exmouth and told the gurues of Camberdown Terrace of the plan. Mr. R immediatly organised an extra special committee meeting to have them banned. Thats why the very complicated rule for centreboards rotating around a pin exists. Spud thought that a dagger board would not be suitable foe sailing in places like the Exe estuary. Interestingly, he was the Laser agent for Devon at the time and they seemed to flourish using them. It was a great pity that the fleet were not able to try them out and I feel the fleet was held back from some real developement which is what a restricted class is all about. The name 'Substitute' was used because we had to take out the daggerboard casing and substitute a normal centreboard case. She had one other innovation which was the bicycle frame vang which worked really well until my engineering broke at Salcombe week in 1980.

The bicycle frame vang is visible in Merlin Rocket book in the rather splendid picture of you sailing out towards the bar - presumably before it broke!

You didn't anticipate any problems short tacking up the Mill bay shore with a dagger board, then?

Measurement from the inside of the top of the transom.

Thanks

ALl I nee dnow is how far from the shoulder of the mast foot to the top of the first black ring ?

Anyone ?

Many thanks again for the quick responses and help

Conor

The shroud triange doesn't matter, when i measured 67 boats at one champs, there was no common traigle the only identical measurement was the 2730 from transome to mast (most of the boats were in a 10cm circle) ans the jib luff also varied around a 10cm line. so where you put them is more down to structual strenght, than measurement.

ps, go on ebay an buy an a4 sheet of tufnol, and let it into the deck under the shroud and lowers fittings, for extra strenght.
Dave.

Coner, on the drawing I sent you it depends on the "other" measurement from the shearline to the shoulder of the mast foot. together they need to be between 630mm and 730mm...

Sorry forgot to say...

Most boats are at the maximum (within 1 or 2mm) I believe...

Hi

So it varies between masts ?

C

Yes the mast length depends on the where it is mounted in relation to the shearline. So for a deck mounted mast you have to add the distance between the shearline and the top of the mast step (could be any convenient point) and the distance from the shoulder of the mast foot (which sits directly on top of the mast step) to the top of the lower black/white band on the mast. The measurement is from the shearline to the band on the mast 630mm min to 730mm max.
The length of the mast will differ depending on the rise of the deck above the shearline. If the rise is small the mast will be longer, if the rise is bigger then the mast will be shorter...

The very reason why with a really flat deck on Gannet I had to put a block under the mast on the deck to get my sheerline - lower black band measurement legal!! Obviously the mast I got second hand (thanks to Mike Hendy) had come from a curvy decked model.

I don't think anyone would have protested you Garry!

...woof!

You just never know Mags - better safe than sorry (but I will admit that before I raised the mast slightly I was getting fed up almost having my life jacket ripped off my back every time we tacked because the boom was so low!)

Then try a Finn Garry, like going about under enemy barbed wire!

If Barry is relieved then so am I, I am surprised that with so many opinions shared and argued that no-one has been prepared to try something different, but then new MR's seem so expensive it would be an expensive error.When Barry and I were sailng MR's they cost even the superdooper deluxe about the same as a very small family car now if the prices quoted are accurate and I'm sure they are its a decent medium to large saloon.

OK Dinghy also

I am considering building a modern Merlin here in Italy. It's a bit of an uphill battle what with one thing and another. Could anyone please describe the best method of constructing the hog, kingpost, deck structure and mast step for a modern carbon deck stepped rig. Also, if anyone knows of any articles or references regarding the above for deck stepped masts for sailing dinghies, particularly Merlins, (even PhD theses) I would be extremely grateful.

Thanks. Ainslie French

Keith Callaghan might be a good bet.